Fluid seal for piston of rotary piston mechanism

ABSTRACT

THE APEX FLUID SEAL ASSEMBLY FOR A ROTARY PISTON MECHANISM COMPRISES, IN COMBUSTION WITH AN APEX SEAL BLADE AND AT LEAST ONE SIDE SEAL STRIP, AN APEX SEAL PIN FORMED TO PROVIDE A REDUCED DIAMETER PORTION DIMENSIONED TO INTERSECT THE INNER SURFACE OF THE SIDE SEAL STRIP GROOVE IN THE ROTARY PISTON IN SUBSTANTIALLY TANGENTIAL RELATIONSHIP ON ONE SIDE OF THE APEX SEAL BLADE SO THAT THE SIDE SEAL STRIP OVERLAPS THE PIN AND ENGAGES THE SAID REDUCED DIAMETER PORTION IN A SEALING LINE CONTACT AND ABUTS THE SHOULDER FORMED BY THE REDUCED DIAMETER PORTION.

July 4, 1972 J. LARRINAGA -TAL 3,674,384

FLUID SEAL FOR PISTON OF ROTARY PISTON MECHANISM Filed March 30, 1971 2 Sheets-Sheet 1 INVENTORS. Ja /v [/MP/A/AG/I BY (HA/P455 Jon/5 July 4, 1972 J. LARRINAGA T FLUID SEAL FOR PISTON OF ROTARY PISTON MECHANISM Filed March 30, 1971 2 SheetsSheet 2 .75 INVENTORS Ja /v ZA/PIP/A/AGfl [HA/P166 JU/VEJ ATTORNEY 3,674,384 Patented July 4, 1972 ABSTRACT OF THE DISCLOSURE The apex fluid seal assembly for a rotary piston mechanism comprises, in combination with an apex seal blade and at least one side seal strip, an apex seal pin formed to provide a reduced diameter portion dimensioned to intersect the inner surface of the side seal strip groove in the rotary piston in substantially tangential relationship on one side of the apex seal blade so that the side seal strip overlaps the pin and engages the said reduced diameter portion in a sealing line contact and abuts the shoulder formed by the reduced diameter portion.

DISCLOSURE This invention relates to fluid seals and, more particularly, to seal means for the piston of a rotary piston mechanism, such as rotary piston, internal combustion engines, compressors, blowers, and pumps or the like.

BACKGROUND OF THE INVENTION Still more specifically, the present invention has particular application to an improved seal means for the apex portion of the rotary piston of an internal combustion engine, such as exemplified in the US. Pat. No. 2, 988,065 which issued to F. Wankel et a1. and US. patent to Bentele et al., No. 3,007,460. During the period of more than a decade following the invention disclosed in the aforesaid Wankel et a1. patent, a continual effort has been made to improve the fluid seal between the rotor and engine housing as is evidenced by the following patents: 2,979,042, 3,033,180, 3,102,518, 3,127,096, 3,139,233, 3,142,439, 3,171,587, 3,180,560, 3,180,561, 3,180,562, 3,193,189, 3,196,849, 3,400,691.

In order to achieve a desired low level of fuel consumption particularly at low r.p.m. of a rotary piston internal combustion engine, the working chambers defined between the housing and rotary piston must be made as fluid tight as possible. This requires that the apex seal blades, the end or side seal strips, and the seal means at the juncture of the apex blade and side seal strips must provide an effective seal to minimize fluid leakage from a working chamber having a high fluid pressure to a chamber of lower fluid pressure or into the lubricating system of the engine from the side faces of the piston. As was recognized in the patents to Froede, No. 3,142,- 439, and Anderson, No. 3,102,518, improved fluid sealing could be achieved by cutting one or two steps or shoulders in the outer face of the apex seal pin so that the end portion of the side seal on the trailing side and/or on the leading side of the apex seal blades overlap and abut the seal pin. It has, however, been found difficult and expensive to accurately machine the one or more steps or shoulders in the apex seal pin so that the curved chordal surface of the step lies in co-planar relation to the arcuate groove into which each of the side seal strips is receivable. It also has been found that fretting corrosion occurs between the pin and the overlapping side seal strip as the apex seal pin rotatively moves under the urging of the apex seal blade as the latter tilts with the fluid pressure changes which occur on opposite sides of the apex seal blade as the rotary piston rotates.

It is, therefore, an object of this invention to provide an improved apex seal assembly having an overlapping seal joint or joints between a side seal strip and apex seal pin, which assembly is quickly and easily fabricated without the need for the former high precision machining operation.

Another object of the present invention is to provide an apex seal assembly in which sealing elfectiveness of the overlapping seal joint is maintained between the side seal strip and the apex seal pin upon slight rotative movement of the apex seal pin relative to the side seal.

A further object of this invention is to provide an apex seal assembly in which fretting corrosion of the side seal strip and apex seal pin is minimized.

A still further object of the present invention is to provide, in an apex seal assembly, an apex seal pin which is interchangeable with other apex seal pins and usable in any apex portion of a rotary piston.

SUMMARY OF THE INVENTION Accordingly, the present invention contemplates a novel apex seal assembly for a rotary piston mechanism comprising, in combination with an apex seal blade and side seal strips, an apex seal pin. The apex seal pin is a cylindrical member which has a longitudinally extending radial slot therein for slidably receiving therein the apex seal blade and a reduced diameter portion adjacent the outer end thereof. The reduced diameter portion is dimensioned so that the annular surface of the reduced diameter portion lies in substantially tangential relationship with the inner surface of at least one of the side seal grooves in the end or side wall of the rotary piston so that the side seal strip, receivable in that side seal groove, engages the seal pin along a line contact and abuts the annular shoulder formed by the reduced diameter portlon.

In another embodiment of this invention, the apex seal pin is constructed of two cylindrical members of different diameters concentrically arranged with the smaller diameter cylinder projecting beyond the end of the larger cylinder to thereby form the reduced diameter portion according to this invention. The two cylindrical members may be tubular or the inner, smaller diameter tube of solid construction Without departure from the spirit and scope of the invention.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an end fragmentary elevational view of a conventional apex seal assembly over which the present invention constitutes an improvement;

FIG. 2 is a view similar to FIG. 1 showing the apex seal assembly according to this invention;

FIG. 3 is a cross sectional view taken along line 33 of FIG. 2 on a somewhat reduced scale;

FIG. 4 is a fragmentary view in perspective of the apex seal assembly shown in FIG. 2;

FIG. 5 is a perspective view of the apex seal pin according to this invention;

FIG. 6 is a fragmentary view, similar to FIG. 4, showing an apex seal assembly according to another embodiment of the invention; and,

FIG. 7 is an exploded view in perspective of the apex seal pin according to the embodiment illustrated in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to the drawings and, more specifically, FIGS. 2, 3, 4 and 5, the reference number 10 generally designates the apex seal assembly according to one embodiment of the present invention. The apex seal assembly is shown and will be described in connection with a rotary piston 12 of a rotary piston internal combustion engine, such as disclosed in the US. patents to Wankel et al., No. 2,988,065 and Bentele et al., No. 3,007,460. It is, however, to be understood that the invention has application to a broad range of other devices where fluid sealing in multiple planes is required between a rotating member and a stationary member, such as in fluid motors, compressors and pumps.

The apex seal assembly 10 comprises an apex seal blade 14, two side seal strips 16 and 18, and a novel apex seal pin 20 according to this invention carried in each of the apex portions (only one of which is shown) of rotary piston 12.

The apex seal blade 14 may be a single blade as shown in the US. Patent No. 3,180,562 to Bentele or preferably comprise a plurality of elements, such as disclosed in U.S. patents to Anderson, No. 3,102,518, Jones, No. 3,300,124 and Jones, No. 3,400,691, which blade is slidably mounted in a radial slot 22 in the apex portion of rotary piston 12, slot 22 communicating with a cylindrical recess 30 in which apex seal pin 20 is inserted. As shown in FIG. 3, a spring 15 is disposed between the bottom of recess 30 and apex seal blade 14 to bias the latter outwardly so that the distal tip end of apex seal blade 14 maintains contact with the coated trochoidal surface 17 of the housing 19 as rotary piston 12 rotates in the direction indicated by the arrow.

Each of the side seal strips 16 and 18 are slidably receivable in a groove 24 and 26, respectively, each of which is formed in the side surface of rotary piston 12 and extends between next adjacent apex portions of the rotary piston and in communication at opposite ends with slot 22. A suitable spring means, such as an annular wavy spring 28 (see FIG. 4), is disposed in each of the grooves 24 and 26 to bias the side seal strip out of their respective grooves into contact with the end wall surface 25 (see FIG. 3) of the engine housing 19.

The apex seal pin is a cylindrical member disposed in cylindrical recess 30 formed to extend inwardly from the side surface of rotary piston 12 and in communication with slot 22 at the diametrical line of the recess. The seal pin 20 is provided with a longitudinally extending radial groove 32 which is positioned in alignment with slot 22 so that the inner end portion of apex seal blade 14 projects into groove 32. The recess 30 is also located to communicate with grooves 24 and 26 so that side seal strips 16 and 18 engage apex seal pin 20. As shown in FIG. 3, seal pin 20 is dimensioned in length so that a space is defined by its inner end and recess 30, in which space spring 15 is disposed. Seal pin 20 is biased outwardly toward the side wall surface (see FIG. 3) of the engine housing 19 by gaseous fluid pressure in the space behind the seal pin and/or spring means, such as spring 15. The apex seal pin 20 coacts with apex seal blade 14 and side seal strips 16 and 18 to effect a fluid seal in the area of the juncture of the side seal strips and apex seal blade 14.

As shown in FIG. 1, the prior art recognized that a more effective seal is achieved by providing the apex seal pin 20A, similar to apex seal pin 20 according to this invention, with at least one step or shoulder 34 disposed inwardly of the end bearing surface to form a curved, generally chordal surf-ace lying in coplanar relationship with the inner or lower surface of side seal strip groove 24A. This chordal step 34 permits the end portion of side seal strip 16A to overlap and abut the chordal surface of step 34 in surface-to-surface contact. Thus, gaseous fluid is prevented from passing between the interstice between the apex seal blade 14A and the end 36 of side seal strip 24A into the space adjacent the central area of rotary piston 12 by the surface-to-surface contact between the chordal surface of step 34 and side seal strip 16A. While this arrangement was found to produce an improved seal, it was found difficult and, hence,

expensive to machine the chordal step 34 so that the chordal surface and the inner surface of side seal strip grooves 24A extended in co-planar relationship. It was also discovered that, as apex seal blade 14A tilted in slot 22A under change in gaseous fluid pressure on opposite sides of the blade during rotation of rotary piston 12A in the direction indicated by arrow A, the torque imposed by the lower end of seal blade 14A on the seal pin caused seal pin 20A to slightly rotate within the limits permitted by the tolerances between the various elements of the apex seal assembly. This relative movement between the chordal surface of step 34 and side seal strip 16A caused wear or fretting corrosion of both members and, hence, reduction in the effective operative life of the apex seal assembly. Accordingly, the present invention contemplates, as shown in FIGS. 2 to 7, the novel apex seal pin 20 which overcomes the aforementioned disadvantages of the prior art structures.

As best shown in FIGS. 2 to 5, apex seal pin 20 is provided, at its outer end portion, with a reduced diameter portion 38. The diametric dimension of portion 38 is selected to meet the lower surface of side seal groove 24 in substantial tangential relation so that side seal strip 16 engages the surface of reduced diameter portion 38 in a line contact. The length of reduced diameter portion 38 is dimensioned so that, when side seal strip 16 abuts the shoulder 40 formed by the reduced diameter portion, the outer surface of the side seal strip 16 lies in substantial co-planar relationship with the end bearing surface 42 of apex seal pin 20 (see FIG. 4). Since only line contact between side seal strip 16 and reduced diameter portion 38 of seal pin 20 is required, a lesser degree of machining accuracy is required than in the prior art apex seal assembly such as shown in FIG. 1. Also, the apex seal pins are interchangeable, whereas the apex seal pins 20A of the prior art apex seal assemblies had to be matched or mated to the groove 24 and, therefore, could be used only in association with the mated groove.

As shown in FIGS. 2 and 4, the side seal groove 18 is preferably formed in rotary piston 12 so that the end of the side seal strip 18, which is disposed in groove 18, abuts the reduced diameter portion 38 at a point B somewhat diametrically opposite the point of line contact between seal strip 16 and reduced diameter portion 38 of seal pin 20. However, without deviating from the spirit and scope of the present invention, it is contemplated that side seal groove 26 can be so located that it meets the reduced diameter portion 38 substantially tangentially in the same manner as groove 24. In this arrangement, side seal strip 18, which is receivable in side seal groove 26, is dimensioned so that it overlaps and abuts, in a line contact, reduced diameter portion 38.

ALTERNATIVE EMBODIMENT In FIGS. 6 and 7 of the drawings, an apex seal assembly 44, according to another embodiment, is illustrated. It differs from apex seal assembly 10 in that the reducing diameter portion of the apex seal pin is formed by two telescopically arragned cylindrical members instead of forming such reduced diameter portion from a single cylinder as is seal pin 20 herein described and shown in FIGS. 2 to 5. In apex seal assembly 44 the ease of machining is further improved and, hence, is less expensive to fabricate and assemble. It also increases the elfectiveness of the assembly by eliminating the small radius fillet at shoulder 40 that is formed in machining reduced diameter portion 38 and the slight leakage flow path formed between such fillet and the chamfer which is desirable on the inner, internal diameter edge portion of side seal strip 16.

The apex seal assembly 44 includes an apex seal pin 45 which comprises an outer cylindrical member 46 having an axial bore 48 therein and in which is disposed an inner cylindrical member 50. The telescopically arranged outer and inner cylindrical members 46 and 50 each have a longitudinally extending slot 52 and 54, respectively, which are disposed in registry with each other and a slot 56 in the rotary piston to receive an apex seal blade 58 in the same manner that groove 32 receives apex seal blade 14 of apex seal assembly 10. The inner cylindrical member 50 is dimensioned to fit within bore 48 of cylindrical member 46 in a tight interference relationship and positioned so that its outer, distal end projects beyond the outer end of cylindrical member 46 to thereby form a reduced diameter portion 60 and shoulder 62, similar to reduced diameter portion 38 and shoulder 40 of apex seal pin 20. In assembly, the inner cylindrical member 50 can be axially positioned in bore 48 by forceably moving member 50, as by impact blows delivered to the outer end of member 50 until the side seal strip 64, similar to side seal strip 16, lies in abutment against shoulder 62 and its outer surface lies in co-planar relationship with the outer surface of member 50. Thus, in this simple manner the dimension or depth of reduced diameter portion is determined to thereby obviate the heretofore required exacting machining operation. Also, as a further simplification of fabrication, only slot 54 in inner cylindrical member 50 need be accurately dimensioned to embrace apex seal blade 58, the slot 52 in outer cylindrical member 46 forming with apex seal blade 58 a sloppy fit.

The above described two-piece apex seal pin assembly is disposed in a cylindrical recess 66, similar to recess 30 for seal pin 20, in the apex portion of a rotary piston 68. The recess 66 is located so that the outer surface (reduced diameter portion) of inner cylindrical member 50 meets, in substantial tangential relationship, the seal groove in which side seal strip 64 is disposed. This provides, as in apex seal assembly '10, a line contact between side seal strip 64 and the outer surface of cylindrical member 50. As previously described with regard to apex seal assembly 10, the inner and outer cylindrical members 46 and 50 biased outwardly by gaseous fluid pressure or spring means toward the adjacent housing side wall (not shown) so that the end of inner cylindrical member 50 is maintained in contact with the housing side wall (not shown) as the rotary piston rotates. Simultaneously, the end outer cylindrical member 46 is held by the gaseous fluid pressure in contact with the inner surface of side seal strip 64 to thus provide another seal point. Of course, apex seal blade 58 is biased outwardly of groove 56 in rotary piston by a spring (not shown), similar to spring 15 (FIG. 3), disposed in recess 66. Because both the inner and outer cylindrical members 46 and 50 tightly fitted together and are biased outwardly, one against the wall and the other against the side seal strip, the lengths of the inner and outer cylindrical members may be the same or different. That is, the inner cylindrical member 50 need not be longer in length than outer cylindrical member 46 to provide a reduced diameter portion according to this invention.

As described with respect to apex seal assembly 10, apex seal assembly 44 may be constructed and arranged so that the side seal strip 70 either preferably abuts at its end the outer surface of inner cylindrical member 50 at a point somewhat diametrically opposite the line contact of side seal strip 64 of cylindrical member 50 or overlaps and abuts, in a line contact, the outer surface of cylindrical member 50 in the same manner as side seal strip 64 contacts the cylindrical member.

In an alternative construction (not shown), inner cylindrical member 50 may be of solid construction with a longitudinal slot therein rather than a tubular member without departing from the scope and spirit of this inventiOn.

It is believed now readily apparent that the apex seal assembly, according to this invention, provides a fluid seal for a rotary piston mechanism which is relatively easy to fabricate and install and, yet, provides an effective seal. It is an apex seal which has a relatively long operative life by eliminating wear or fretting corrosion between the side seal strips and apex seal pin. It is an apex seal assembly in which the apex seal pin is not mated to the side seal strip which it is to engage so that it has an interchangeability characteristic.

Although several embodiments of the invention have been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

1. An apex seal assembly for each of the apex portions of a rotary piston hlaving side walls and peripheral surfaces connecting each of a plurality of apex portions comprising an apex seal pin assembly disposed in a recess in a side wall of the piston in combination with apex seal blade means disposed for reciprocative movement in a radially extending groove in an apex portion and at least one side seal strip disposed for slidable movement in a groove formed in said side wall surface of the rotary piston and extending between next adjacent apex portions, the apex seal pin assembly comprising:

(a) cylindrical body means disposed in said recess in the rotary piston;

(b) extension means coaxially extending from said cylindrical body means having a bearing end surface disposed beyond the plane of the rotary piston side .wall and forming with said cylindrical body means an annular reduced diameter portion and an annular shoulder spaced inwardly of the bearing surface;

(c) the reduced diameter portion being dimensioned in diameter to communicate with the inner surface of said side seal strip groove on one side of the apex seal blade means so that the side seal strip receivable in the seal strip groove abuts the surface of said re duced diameter portion in a line contact;

(d) the reduced diameter portion being dimensioned so that the inner surface of said side seal strip abuts the shoulder and its outer surface lies in substantial coplanar relationship with said bearing surface of said extension means.

2. The appanatus of claim 1 wherein said cylindrical body means is a solid member and said extension means is formed by reducing the diameter of the end portion of said body means.

3. The apparatus of claim 1 wherein said cylindrical body means is tubular land said extension means is cylindrical and axially receivable in one end of the cylindrical body means so the bearing end surface lies in a plane spaced from said end of the cylindrical body means to thereby [form said reduced diameter end portion and said annular shoulder.

4. The apparatus of claim 3 wherein said extension means is a tubular member.

5. The apparatus of claim 3 wherein said extension means is in interference fit with the cylindrical body means so that in normal use there is no relative movement between the extension means and cylindrical body means.

6. The apparatus of claim 1 wherein said one side seal strip is disposed adjacent the trailing side of said apex seal blade means and said combination includes a second side seal strip disposed for slidable movement in a groove formed in said side wall surface of the rotary piston adjacent the leading side of the apex seal blade means.

7. The apparatus of claim 6 wherein the end of said second side seal strip abuts the surface of reduced diameter portion in an area generally diametrically opposite the line contact of said one side seal strip.

8. The apparatus of claim 1 wherein said cylindrical body means and the extension means each has a longitudinally extending slot which register with each other and said radially extending groove in the apex portion of the rotary piston and each slot dimensioned to receive the lower end portion Otf said apex seal blade means.

9. The apparatus of claim 1 wherein said cylindrical body means is tubular and said extension means is cylindrical and axially receivable in one end of the cylindrical body means so that the bearing end surface lies in a plane spaced from said end of the cylindrical body means to thereby form said reduced diameter end portion and said annular shoulder, said tubular, cylindrical body means and cylindrical extension means being each provided with a longitudinally extending slot which registers with each other and said radially extending groove in the apex portion of the rotary piston, said slot in said cylindrical body means being dimensioned to receive the lower end portion of said apex seal blade therein in a loose fit While the slot in said cylindrical extension means is dimensioned to receive the lower end portion of said apex seal blade in tight fitting relationship.

10. The apparatus of claim 9 wherein said cylindrical extension is tubular.

11. The apparatus of claim 9 wherein said cylindrical extension means is a solid member.

References Cited UNITED STATES PATENTS CARLTON R. CROYLE, Primary Examiner I. J. VRABLIK, Assistant Examiner US. Cl. X.-R. 4 1 81 42 UNITED STATES PATENT OFFICE- QER'HFICATE CF GCRRECTIQN Patent No. 3,674,384 Dated July 4, 1972 Inventor(s) John Larrinaga and Charles Jones It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICATION:

Column 4, line 60, the word "arragned" should be --.arranged.

line 66, before the first word "effectiveness" insert the word --sealing.

Column 5, line 37, after the number "50" add the word --are--.

IN THE CLAIMS: J i

.lUlu

Column 7, line 2, the word "r eec ive" should read -receive--.

line 15 the word "reeoive" should read --receive-.

Column 8, line 2, after the word "extension" insert the word -means--.

Signed and sea led this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. I y ROBERT GOTTSCHALK Attesting Of-fioer I g I Commissioner of Patents 

